Weather and soil in the US Midwest influence the effectiveness of single- and split-nitrogen applications in corn production

Splitting the N application into two or more timings may improve corn (Zea mays L.) grain yield and N recovery relative to a single-N application. A 49 site-year study across eight U.S. Midwestern states compared the effect of an at-planting (single-N application) and two split-N applications [45 (45+SD) or 90 kg N ha⁻¹ (90+SD) at planting with the remainder of the total rate (180 or 270 kg N ha⁻¹) applied at V9]. For split-N applications, soil and plant responses were similar between 45+SD and 90+SD 93–98% of the time, indicating the at-planting N rate of 45 kg N ha⁻¹ may be all that is needed in most cropping scenarios. Splitting the N application compared to a single-N application changed soil NO₃–N at VT and post-harvest <35% of the time and plant N uptake and grain yield <15% of the time. Split-N applications had greater grain yield in areas with uniform precipitation around the sidedress timing (Shannon Diversity Index >0.56–0.59) to incorporate N in the root zone, and in coarse-textured soil (sand content >4–10%) that had greater potential for N loss. Single-N applications produced greater grain yield in soils with more total N (>2.1–2.4 g kg⁻¹) to support N mineralization and greater cation exchange capacity (CEC) (> 27–31 cmol_c kg⁻¹), silt content (>66–74%), or clay content (>24–37%) to improve nutrient and water retention. Decisions on nitrogen application timing should be made based on soil parameters and typical weather conditions around the sidedress timing.